KR20160030442A - Apparatus and method for mitigating interference in a wireless communication system - Google Patents

Abstract

The present invention relates to a pre-5G or 5G communications system to be provided for supporting higher data rates after a 4G communications system such as LTE. The present invention relates to a device for mitigating interference in a wireless communications system and a method thereof. A method for operating a network device comprises the following operations of: eliminating a target signal of a target bandwidth (BW) from a receiving signal; estimating a parameter related to interference based on the receiving signal from which the target signal is eliminated; estimating an interference signal based on the parameter related to the interference; and eliminating the interference signal from the receiving signal.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and method for interference mitigation in a wireless communication system,

The present invention relates to an apparatus and method for interference mitigation in a wireless communication system.

Efforts are underway to develop an improved 5G or pre-5G communication system to meet the growing demand for wireless data traffic after commercialization of the 4G communication system. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (Beyond 4G network) communication system or after a LTE system (Post LTE).

To achieve a high data rate, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands (e.g., 60 gigahertz (60GHz) bands). In order to mitigate the path loss of the radio wave in the very high frequency band and to increase the propagation distance of the radio wave, in the 5G communication system, beamforming, massive MIMO, full-dimension MIMO (FD-MIMO ), Array antennas, analog beam-forming, and large scale antenna technologies are being discussed.

Further, in order to improve the network of the system, the 5G communication system has developed an advanced small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network (D2D), a wireless backhaul, a moving network, a cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation ) Are being developed.

In addition, in the 5G system, the Advanced Coding Modulation (ACM) scheme, Hybrid FSK and QAM Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), the advanced connection technology, Filter Bank Multi Carrier (FBMC) (non-orthogonal multiple access), and SCMA (sparse code multiple access).

In 3GPP LTE, a base station (BS) transmits an uplink (UL) data signal from a subscriber station located in its BS range as well as a subscriber terminal belonging to another BS . In order to decode the uplink data signal, the BS needs to distinguish a desired signal from an interfering signal.

Accordingly, embodiments of the present invention are intended to provide an apparatus and method for effectively distinguishing between a desired signal and an interference signal.

Embodiments of the present invention also provide an apparatus and method for efficiently determining a search space for generating an interference signal.

Embodiments of the present invention also provide an apparatus and method for efficiently reducing search space based on the number of interferers for a resource block of bandwidth.

According to various embodiments of the present invention, a method of operating a network device includes the steps of removing a target signal of a target bandwidth (BW) from a received signal, determining parameters related to interference based on the received signal from which the target signal is removed Estimating an interference signal based on the parameter related to the interference, and removing the interference signal from the received signal.

In accordance with various embodiments of the present invention, a network device is configured to remove a target signal of a target bandwidth (BW) from a received signal, estimate parameters related to interference based on the received signal from which the target signal is removed, And a processor for estimating an interference signal based on the parameters related to the received signal and removing the interference signal from the received signal.

Embodiments of the present invention can efficiently distinguish a desired signal from an interference signal.

In addition, embodiments of the present invention can efficiently distinguish a desired signal from an interference signal by efficiently determining a search space for generating an interference signal.

In addition, embodiments of the present invention can efficiently distinguish a desired signal from an interference signal by efficiently reducing the search space based on the number of interferers for a bandwidth resource block.

1 is a diagram illustrating a wireless network in accordance with various embodiments of the present invention.
2A and 2B are diagrams illustrating wireless transmission and reception paths in accordance with various embodiments of the present invention.
3A is a block diagram of a user device according to various embodiments of the present invention.
3B is a block diagram of a BS according to various embodiments of the present invention.
4 is a diagram illustrating a wireless uplink transmission in a wireless network according to various embodiments of the present invention.
FIG. 5 is a block diagram of an overall Blind Interference Sensing (BIS) and an IC (Interference Cancellation) algorithm according to various examples of the present invention.
6 is a diagram illustrating a plurality of candidate interference BWs in accordance with various embodiments of the present invention.
7 is a flowchart illustrating a partial space BIS algorithm according to the first embodiment of the present invention.
FIG. 8 is a flowchart illustrating a partial space BIS algorithm according to a second embodiment of the present invention.
Figures 9a and 9b are diagrams for detecting energy in a BW according to various embodiments of the present invention.
Figure 10 is a flow diagram that extends the PRB in the subspace BIS algorithm according to various embodiments of the present invention.
11A and 11B are diagrams for detecting an interference case in various embodiments of the present invention.
12 is a diagram for determining a set of subspace interference BWs according to a first embodiment of the present invention.
13 is a diagram for determining a set of subspace interference BWs according to a second embodiment of the present invention.
14A is a diagram illustrating an invalid case mapping according to various embodiments of the present invention.
14B is a diagram illustrating a continuous BW decision according to various embodiments of the present invention.
14C is a diagram illustrating all interferor departure mapping in accordance with various embodiments of the present invention.
FIG. 15 is a view showing a snapshot of an algorithm reflecting three issues according to the options C-1, C-2, and C-3 according to various embodiments of the present invention.
16 is a diagram illustrating two variations of an algorithm according to various embodiments of the present invention.
17 is a flow chart of the DMRS algorithm according to various embodiments of the present invention.
18 is a graph illustrating the reduction of the DMRS search space in accordance with various embodiments of the present invention.
19 is a graph showing that the correct interference BW according to various embodiments of the present invention is included in a reduced subspace with a probability close to unity.
20 is a graph illustrating the detection probabilities of three DMRS sequences corresponding to three interferers in accordance with various embodiments of the present invention.
21 is a diagram illustrating a valid interference case and an invalid interference case according to various embodiments of the present invention.
FIGS. 22A through 22D are diagrams illustrating a map index tuple corresponding to a valid interference case according to an embodiment of the present invention. FIG.

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings. It should be understood, however, that the techniques described herein are not intended to be limited to any particular embodiment, but rather include various modifications, equivalents, and / or alternatives of the embodiments of this document. In connection with the description of the drawings, like reference numerals may be used for similar components.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the other embodiments. The singular expressions may include plural expressions unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art. The general predefined terms used in this document may be interpreted in the same or similar sense as the contextual meanings of the related art and, unless expressly defined in this document, include ideally or excessively formal meanings . In some cases, even the terms defined in this document can not be construed as excluding the embodiments of this document.

1 is a diagram illustrating a wireless network in accordance with various embodiments of the present invention. The wireless network 100 shown in FIG. 1 is for the purpose of illustrating the present invention only, and the claims of the present invention are not limited thereto. For example, the present invention may be applied to wireless networks other than the wireless network 100, as long as the scope of the present invention does not depart from the scope of the present invention.

Referring to FIG. 1, a wireless network 100 includes a base station (BS) 101, a BS2 102, and a BS3 103. BS1 101 communicates with BS2 102 and BS3 103. The BS1 101 may also communicate with an Internet Protocol (IP) network, such as at least one Internet, a dedicated IP network, or another data network.

Depending on the type of network, "BS" or "base station" may be used with other well-known terms such as "eNodeB", "eNB", or "access point". For convenience, the term "base station" or "BS" as used in this patent document refers to an infrastructure network component that provides wireless access to a remote terminal. Also, depending on the network type, a "user equipment" or "UE" may be a "mobile station", "subscriber station", "remote terminal", "wireless terminal", "network device" Other well-known terms can be used. For convenience, the terms "user equipment" and "UE" refer to remote wireless equipment that wirelessly accesses a BS in this patent document. The UE may be a mobile device (e.g., a cell phone or smart phone) or a fixed device (e.g., a desktop computer or a vending machine).

BS2 102 provides wireless broadband access to network 130 for a first plurality of user equipments (UEs) located within its coverage area 120. The first plurality of UEs comprises a UE 111 located in a small business (SB), a UE 112 located in an enterprise (E), a UE 113 located in a WiFi Hotspot (HS), a first residence (R) A UE 114 located in a second residence R, a UE 116 that may be a mobile device M such as a cell phone, wireless laptop, wireless PDA, and the like. BS3 103 provides wireless broadband access to network 130 for a plurality of UEs located within its coverage area 125. The second plurality of UEs includes UEs 115, 116. In one embodiment, at least one of BSs 101-103 may communicate with different BSs and UEs 111-116, respectively, using 5G, LTE, LTE-A, WiMAX or other next generation wireless communication technologies. In one embodiment, the network device refers to an element that constitutes a network, for example, a BS or a UE.

1 represents the approximate size of the coverage area 120 and the coverage area 125. As shown in FIG. The coverage area 120 and the coverage area 125 are shown in a circle only for illustration and explanation. Coverage areas associated with BSs, such as coverage area 120 and coverage area 125, may have different shapes, including irregular shapes depending on the configuration of the BSs and the wireless environment, such as natural or artificial obstacles.

At least one of BS1 101, BS2 102, and BS3 103 performs a BIS process according to a blind interference sensing (BIS) algorithm, removes at least one interfering signal determined by the BIS algorithm, / RTI > In one embodiment, the BIS algorithm may be used in another device, such as a user device.

Although FIG. 1 illustrates wireless network 100, various variations may be applied to FIG. For example, the wireless network 100 may include a certain number of BSs and UEs in any suitable arrangement. BS 101 may also communicate directly with a certain number of UEs and may provide the UE with broadband wireless communication access to network 130. Similarly, BS2 102 and BS3 103, respectively, may also communicate directly with network 130 and may provide the UE with broadband wireless communication access to network 130. Further, BS1 101, BS2 102, and / or BS3 103 may provide access to other networks or additional external networks, such as external telephone networks or other types of data networks.

2A and 2B are diagrams illustrating wireless transmission and reception paths in accordance with various embodiments of the present invention. In the following description, transmission path 200 may be implemented within a BS (e.g., BS2 102). On the other hand, the receive path 250 may be implemented within a UE (e.g., UE 116). However, the receive path 250 may be implemented within the BS, and the transmit path 200 may be implemented within the UE as well. In one embodiment, the receive path 250 may decode the received signal from which the interfering signal has been removed after removing at least one interfering signal determined by the BIS algorithm in the received signal.

The transmission path 200 includes a channel coding and modulation unit 205, a serial-to-parallel (S-to-P) conversion unit 210, an Inverse Fast Fourier Transform An IFFT unit 215, a parallel-to-serial converter 220, a cyclic prefix (CP) insertion unit 225, and an up converter (UP) . The reception path 250 includes a down-converter (DC) 255, a CP removal unit 260, a serial-parallel conversion unit 265, an N-sized Fast Fourier Transform (FFT) unit 270, a P- -S) conversion unit 275 and a channel decoding and demodulation unit 280. The channel decoding and demodulation unit 280 includes a channel decoding unit and a channel decoding unit.

In the transmission path 200, the channel coding and modulation unit 205 receives and codes information (in units of bits) (for example, using a low-density parity check (LDPC) scheme) (E.g., quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM)) to generate a sequence of modulation symbols on the modulation symbol . The serial-to-parallel conversion unit 210 converts the serial modulation symbols into parallel data to generate N parallel symbol streams (such as de-multiplex). Here, N denotes the size of the IFFT / FFT unit used in BS2 102 and UE 116. [ The IFFT unit 215 having the N size performs an IFFT operation on the N parallel symbol streams to generate an output signal in the time domain. The parallel-to-serial converter 220 converts the time-domain parallel output symbols output from the N-sized IFFT unit 215 into a serial signal to generate a time-domain serial signal (such as a multiplex). The CP inserting unit 225 inserts the cyclic prefix into the serial signal in the time domain. The up converter 230 converts the signal output from the CP inserter 225 to an RF frequency for transmission over the wireless channel. Here, the signal can be filtered in the base band before being converted to RF frequency.

The RF transmission signal transmitted from the BS2 102 is received by the UE 116 over the radio channel and the opposite operation of the operation performed at the BS2 102 is performed at the UE 116. [ Downconverter 255 downconverts the received RF transmit signal to a baseband frequency. CP rejection 260 removes the periodic prefix signal from the baseband transmitted signal to produce a serial time-domain baseband signal. The serial-to-parallel converter 265 converts the time-domain baseband signal into parallel time-domain signals. The N-sized FFT unit 270 performs an FFT algorithm on the parallel time-domain signals to generate N parallel frequency-domain signals. The parallel-to-serial converter 275 converts the parallel frequency-domain signals into a sequence of modulated data symbols. The channel decoding and demodulation unit 280 demodulates and decodes the modulated symbols to recover the original input data stream.

Each of BS1 101, BS2 102, BS3 103 may implement a transmit path 200 similar to downlink transmission to UEs 111-116 and implement a receive path 250 similar to the uplink reception from UEs 111-116 . Similarly, each of the UEs 111-116 may implement transmit path 200 for uplink transmissions to BS1 101, BS2 102, BS3 103 and receive path 250 for downlink reception from BS1 101, BS2 102, Can be implemented.

Each of the components shown in Figs. 2A and 2B may be implemented using only hardware or a combination of software / firmware and hardware. For example, at least some of the components in FIGS. 2A and 2A may be implemented in software, while other components may be implemented in any combination of hardware, software, and possible hardware. For example, the FFT unit 270 and the IFFT unit 215 may be implemented with possible software algorithms, and the value of N may be changed according to the implementation.

Although the present invention has been described by using FFT and IFFT, this is merely an example and does not limit the scope of the present invention. In the present invention, other types of transforms such as a Discrete Fourier Transform (DFT) or an Inverse Discrete Fourier Transform (IDFT) function may be used. While the value of the variable N used in the DFT or IDFT function is an integer number (e.g., the same number as 1, 2, 3, 4), the value of the variable N for the FFT or IFFT function is 2 (E.g., the same number as 1, 2, 4, 8, 16).

Although FIGS. 2A and 2B illustrate wireless transmission and reception paths, various modifications may be attempted within FIGS. 2A and 2B. For example, the various components of FIGS. 2A and 2B may be combined, partitioned, or omitted, and additional components may be added according to specific needs. 2A and 2B illustrate examples of transmission and reception type paths that can be used in a wireless network, but do not limit the scope of the present invention. Any other suitable structure may be used to support wireless communication in a wireless network.

3A is a block diagram of a user device according to various embodiments of the present invention. The user equipment (e.g. UE 116) shown in FIG. 3 is only an example, and the UEs 111-115 shown in FIG. 1 may have the same or similar form as the block configuration of FIG. However, the UE has various forms, and Fig. 3A does not limit the scope of the present invention to the specific structure of the UE.

3A, the UE 116 includes an antenna 305, a radio frequency (RF) transmission and reception unit 310, a transmission (TX) processing unit 315, a microphone 320, and a reception (RX) processing unit 325. The UE 116 further includes a speaker 330, a main processor 340, an input / output (I / O) interface (IF) unit 345, a keypad 350, a display 355, and a memory 360 do. The memory 360 includes a basic operating system (OS) program 361 and at least one application 362.

The RF transceiver 310 receives an input RF signal transmitted by the network 100 from the antenna 305. The RF transceiver 310 downconverts the input RF signal to generate an intermediate frequency (IF) or baseband signal. Here, the IF or baseband signal is output to the RX processor 325. The RX processing unit 325 generates the processed baseband signal by filtering, decoding, and / or digitizing the baseband or IF signal. The RX processor 325 sends the processed baseband signal to the speaker 330 (e.g., if the processed baseband signal is voice data) or to the main processor 340 for further processing of the processed baseband signal For example, if the processed baseband signal is web browsing data).

TX processing unit 315 receives analog or digital data from microphone 320 or other analog or digital data (e.g., web data, e-mail, or interactive video game data, etc.) from main processor 340. TX processor 315 generates the processed output baseband or intermediate frequency signal by encoding, multiplexing, and / or digitizing the output baseband data to produce a processed baseband or intermediate frequency signal. The RF transceiver 310 receives the processed output baseband or intermediate frequency signal from the TX processor 315, upconverts it to an RF signal, and transmits the RF baseband or intermediate frequency signal through the antenna 305.

The main processor 340 may include at least one processor or processor device and may execute a basic OS program 361 stored in the memory 360 to control the overall operation of the UE 116. [ For example, the main processor 340 controls reception of a forward channel signal and transmission of a reverse channel signal by a RF transmitting / receiving unit 310, a RX processing unit 325, and a TX processing unit 315 according to well-known principles can do. In some embodiments, the main processor 340 includes at least one microprocessor or microcontroller.

The main processor 340 may execute a process or a program stored in the memory 360. For example, the main processor 340 may perform an operation of detecting an interference signal and decoding the received signal from which the interference signal has been removed. The main processor 340 can move data into or out of the memory 360 according to the requirements of a running process. According to one embodiment, the main processor 340 may execute the application 362 in response to a user or a signal received at the BS or based on the OS program 361. The main processor 340 is connected to the I / O interface unit 345, and the I / O interface unit 345 can provide a connection between the UE 116 and another device (e.g., a laptop computer or a portable computer). The I / O interface section 345 is a communication path between the accessory and the main processor 340.

The main processor 340 may be connected to the keypad 350 and the display unit 355. A user of the UE 116 may input data to the UE 116 using the keypad 350. Display 355 may be a liquid crystal display or other display capable of displaying characters and / or at least limited graphics, such as at least a web site.

The memory 360 is connected to the main processor 340. Some of the memory 360 may include random access memory (RAM), and others may include flash memory or other read-only memory (ROM).

Although FIG. 3A illustrates an example of a UE 116, various changes may be applied to FIG. 3A. For example, some of the configurations of FIG. 3A may be combined, disassembled, or omitted, and components may be added as needed. For example, the main processor 340 may be divided into several processors, such as one or more CPUs (Central Processing Unit) or GPU (Graphics Processing Unit). 3A also shows UE 116 as a cell phone or smart phone, but otherwise the UE may be another type of mobile or fixed device.

3B is a block diagram of a BS according to various embodiments of the present invention. The BS (e.g., BS2 102) shown in FIG. 3B is merely an example, and other BSs (e.g., BS1 101, BS3 103) of FIG. 1 may have the same or similar form as the block configuration of FIG. However, the BS may be implemented in various forms, and FIG. 3B does not limit the scope of the present invention to the specific structure of the BS.

3B, BS2 102 includes a plurality of antennas 370a through 370n, a plurality of RF transceivers 372a through 372n, a transmit (TX) processor 374, and a receive (RX) processor 376. BS2 102 includes a processor (or controller) 378, memory 380, and a backhaul or network interface portion 382.

The RF transceivers 372a through 372n receive an incoming RF signal (e.g., a signal transmitted by the UE or another BS) from the antennas 370a through 370n. The RF transceivers 372a through 372n down-convert the received RF signal to generate an IF or baseband signal and transmit the IF or baseband signal to the RX processor 376. RX processor 376 generates the processed baseband signal by filtering, decoding, and / or digitizing the received baseband or IF signal. RX processor 376 transmits the processed baseband signal to processor 378 for further processing.

TX processor 374 receives analog or digital data (e.g., voice data, web data, email, or interactive video game data) from processor 378. TX processing unit 374 generates a processed baseband or IF signal by encoding, multiplexing, and digitizing analog or digital data (baseband data for output). The RF transceivers 372a through 372n receive the processed baseband or IF signals from the TX processor 374, upconvert the processed baseband or IF signals to RF signals, and transmit the RF signals through the antennas 370a through 370n.

Processor 378 includes one or more processors or other processing devices that control the overall operation of BS2 102. For example, processor 378 may control the reception of forward channel signals and the transmission of reverse channel signals via RF transmit / receive units 372a through 372n, RX processing unit 376, and TX processing unit 324 that follow well-known principles. Processor 378 may perform additional functions such as next generation wireless communication functionality. For example, the processor 378 may perform a BIS by a Blind interference Sensing (BIS) algorithm and may decode the received signal from which the interference signal has been removed. Various other functions may be performed within BS2 102 by processor 378. [ In one embodiment, the processor 378 may include at least one microprocessor or microcontroller.

Processor 378 may execute programs or other processes stored in memory 380, such as a basic OS. Processor 378 may move data into or out of memory 380 in accordance with the needs of a running process.

The processor 378 may be coupled to the backhaul / network interface 335. The backhaul / network interface portion 382 provides the capability for the BS2 102 to communicate with other devices or systems through a backhaul connection or over a network. The backhaul / network interface portion 382 may support communication over a suitable wired or wireless connection. For example, if BS2 102 is implemented as part of a wireless terminal communication system (e.g., supporting 5G, LTE, or LTE-A), backhaul / network interface portion 382 may allow BS2 102 to communicate with a wired or wireless backhaul And to communicate with other BS through the connection. When BS2 102 is implemented as an access point, backhaul / network interface portion 382 may enable BS2 102 to communicate over a wired or wireless connection with a wired or wireless local area network or a larger network (e.g., the Internet). The backhaul / network interface portion 382 may include a suitable structure to support communications over a wired or wireless connection (e.g., an Ethernet or RF transceiver).

Memory 380 may be coupled to processor 325. A portion of memory 380 may include RAM, and the other portion may comprise flash memory or ROM. In one embodiment, a number of instructions (e.g., a BIS algorithm) may be stored in memory 380. The plurality of instructions may be implemented such that the processor 378 executes a BIS process and may decode the received signal from which at least one interfering signal determined by the BIS algorithm has been removed.

As described in more detail below, the transmit and receive paths of the BS2 102 (receive paths implemented using the RF transceivers 372a through 372n, the TX processor 374, and / or the RX processor 376) Lt; RTI ID = 0.0 > aggregation. ≪ / RTI >

FIG. 3B shows an example of BS2 102, but various variations can be applied to FIG. 3B. For example, BS2 102 may include any of the components shown in FIG. 3B. For example, the access point may include a large number of backhaul / network interface portions 382, and the processor 378 may support the function of locating data paths between different network addresses. 3B illustrates BS2 102 as including one TX processing unit 374 and one RX processing unit 376, the BS 102 may alternatively include a plurality of TX processing units 374 or a plurality of RX processing units 376 . For example, BS 102 may include one TX processing unit 374 and one RX processing unit 376 per RF transceiver.

4 is a diagram illustrating a wireless uplink transmission in a wireless network according to various embodiments of the present invention. The embodiment shown in Fig. 4 is only for explaining the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

The UL received signal at BS1 101 included in the wireless network 400 includes two desired signals 405 from UE1 410 and two interfering signals from UE2 420 and UE3 420 that transmitted a signal aimed at two neighboring cells BS2 102 and BS3 103 . For example, BS1 101 may receive interference signal 425 from UE2 415 and interference signal 430 from UE3 420. UE1 410 may comprise the same or similar structure as UE 116 shown in FIG. 3A. UE2 415 and UE3 420 may also include a structure similar or similar to UE 116. [

If the power of the received interfering signal is high, decoding of the desired signal will fail. If decoding fails, BS1 101 estimates the dominant interferer and removes the dominant interferer from the received signal before retrying decoding. BS1 101 may repeat this process several times, if necessary. The challenge of BS1 101 is perfect blind interference sensing (BIS) and interference cancellation (IC). BS1 101 needs to predict all the necessary parameters for the IC, where the parameters include the number of dominant interferers (DI), the physical resource block (PRB) allocation of the dominant interferer, the DMRS DeModulation Reference Signal) sequence, channel, modulation order, and the like. The information available at BS1 101 for estimating this parameter may be a received signal with a parameter (e.g., the desired BW associated with the desired signal 405 received from UE1 410).

5 is a block diagram of an overall BIS and IC algorithm according to various examples of the present invention. The embodiment shown in Fig. 5 is only for explaining the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention. Referring to FIG. 5, each iteration of the overall BIS and IC algorithm 500 may comprise three motion blocks. The three motion blocks may be repeated until another cause of interruption occurs, such as when the desired signal is successfully decoded or when the number of decoding attempts is maximized.

)가 수신된 신호(y)에서 제거되고, 그 결과에 따라 생성된 신호(

)가 다음 동작 510을 위해 제2블록으로 출력된다.In the first block, processing and elimination of the desired signal 505 is performed. The initial input for processing and rejecting the desired signal 505 is the desired user information (e.g., desired BW (desired PRB allocation) and received signal y). The main processing of the desired signal processing and rejection 505 is the Estimation, and decoding of the received signal within the desired BW. If the decoding is successful, the algorithm stops. Otherwise, the desired signal

) Is removed from the received signal (y), and the resulting signal

Is output to the second block for the next operation 510.

In the second block, BIS 510 is performed. Using the desired BW and the received signal with the desired signal removed, the BIS 510 estimates interference-related parameters (e.g., interference BW and DMRS sequences for other interferers).

)를 재구성하기 위해 사용된다. 제3블록의 결과에 따라 생성된 신호는 다른 디코딩 시도를 위해 다시 원하는 신호 처리 및 제거 동작 505을 위해 제1블록으로 출력된다. In the third block, the processing and elimination of the interference signal 515 is performed. The estimated interference DMRS sequences in the second block are used to estimate the interference channels and the modulations. These sequences result in an interference signal (< RTI ID = 0.0 >

). ≪ / RTI > The signal generated according to the result of the third block is output to the first block for the desired signal processing and removal operation 505 again for another decoding attempt.

6 is a diagram illustrating a plurality of candidate interference BWs in accordance with various embodiments of the present invention. The example of candidate interference BWs 600 shown in FIG. 6 is only for illustrating the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

, 여기서,

는 원하는 BW의 시작 PRB 인덱스를 의미하고,

는 원하는 BW의 끝 PRB 인덱스를 의미한다.The BIS begins by estimating the interference BWs of the dominant interferers in terms of PRB indexes. To this end, a set of all possible interference BWs I is considered to overlap with at least one PRB of the BW of the desired signal:

, here,

Denotes a start PRB index of a desired BW,

Means the end PRB index of the desired BW.

Since the magnitude of set I in a real system can be large, it is very complex to thoroughly search all candidate interference BWs of I. Therefore, it is necessary to reduce the search space while maintaining close search results. The present invention proposes a subspace based BIS algorithm to reduce interference BW search space. The reduced search space contains the correct interference BWs of the dominant interferers with a high probability (close to 1), and the reduction in complexity is significant compared to the full search.

7 is a flowchart illustrating a partial space BIS algorithm according to the first embodiment of the present invention. The BIS algorithm 510 shown in FIG. 7 is only for illustrating the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

According to one embodiment of the present invention, as shown in FIG. 7, the BIS algorithm is performed with three operations. The energy sensing operation 705 may be performed by comparing the threshold values of the covariance matrices of the covariance matrices of the received signal from which the desired signal has been removed from the different UL PRBs with a threshold value, Detects the presence of interference in the PRBs (or the total number of UL PRBs in the system BW). The subspace BIS operation 710 detects an interference case (described in detail hereinafter) for all possible pairs of consecutive PRBs in the estimated subspace BIS BW, and obtains a set of candidate interference BWs (PRB allocation). Thereafter, the DMRS BIS 715 operation performs interference DMRS sequence detection only of the interference BWs included in the set of candidate interference BWs obtained in the subspace BIS operation 710.

FIG. 8 is a flowchart illustrating a partial space BIS algorithm according to a second embodiment of the present invention. The embodiment of the partial space BIS algorithm 800 shown in FIG. 8 is only for explaining the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

)는 추정된 원하는 채널

및 추정된 원하는 심볼

을 기반으로 생성된다. 원하는 채널은 DMRS 측정으로 추정될 수 있고, 원하는 심볼은 소프트 비트들(LLR(Log Likelihood Ratio)들)로부터 변조 심볼 맵핑에서 추정된다. 재구성된 원하는 신호는 수신 신호(y)에서 제거된다.According to one embodiment of the present invention, the BIS algorithm 510 begins at the desired signal reconstruction 805. [ For example, the desired signal (

) ≪ / RTI >

And an estimated desired symbol

. ≪ / RTI > The desired channel may be estimated by the DMRS measurement, and the desired symbol is estimated in the modulation symbol mapping from soft bits (LLRs). The reconstructed desired signal is removed from the received signal y.

와 원하는 BW

는 전체 UL BW 내부에 있지만 원하는 BW A₀의 외부에 있는 간섭의 존재를 감지하기 위한 에너지 검출 810을 수행하기 위해 사용된다. 에너지 검출 810의 결과는 부분 공간 BIS BW 815이다. 여기서, 부분 공간 BIS BW 815는 원하는 BW(

)와 원하는 BW의 왼쪽(

)과 오른쪽(

)의 UL PRB들의 인덱스들을 포함하는 집합

이 될 수 있다.The resulting signal

And desired BW

Is used to perform energy detection 810 to detect the presence of interference that is within the entire UL BW but outside the desired BW A ₀ . The result of energy detection 810 is subspace BIS BW 815. Here, the subspace BIS BW 815 is a subspace BW

) And the left side of the desired BW

) And right (

Lt; RTI ID = 0.0 > UL < / RTI &

.

825를 출력한다. 여기서, n은 간섭 BW들의 크기를 나타내고, k는 간섭 BW들의 오프셋을 나타낸다.In conclusion, the subspace BIS operation 820 performs interference case detection for each pair of consecutive RBs in the set A, and the set of candidate interference BWs

825 < / RTI > Where n denotes the size of the interference BWs and k denotes the offset of the interference BWs.

835이다. 여기서 u와 n_cs는 후보 간섭 DMRS 시퀀스들의 나머지 두 파라미터들(그룹 ID와 cyclic shift)를 각각 나타낸다.The DMRS BIS operation 830 performs DMRS sequence detection only for candidate interfering BWs. The output of the DMRS BIS operation 830 is a set of DMRS parameters

835. Where u and n _cs represent the remaining two parameters (group ID and cyclic shift) of the candidate interfering DMRS sequences.

Figures 9a and 9b are diagrams for detecting energy in a BW according to various embodiments of the present invention. The embodiments shown in Figs. 9A and 9B are merely illustrative of the present invention, and do not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

In one embodiment, the subspace BIS BW is iteratively extended by at least one PRB to the left of the desired BW, starting at the desired BW, so that the subspace BIS BW can be determined. The extension 905 is based on energy detection using at least one eigenvalue of the covariance matrix for the signal generated by removing the reconstructed desired signal from the received signal in one or more contiguous PRBs starting at the leftmost PRB of the desired BW do. For example, if at least one eigenvalue exceeds a predetermined reference value, it can be determined that interference is present in the consecutive PRBs considered.

), 부분 공간 BIS BW는 PRB(0, -1,

)에서 에너지 검출을 수행함으로써 왼쪽으로 확장된다. 확장 905는 도 9a의 900과 같이, 하나의 PRB에서 고유값이 검출되지 않을 때까지 계속해서 수행된다. 이와 달리, PRB1 920에서 검출된 고유값의 개수가 0이라면(

), 도 9b의 910과 같이, 부분 공간 BIS BW는 왼쪽으로 확장되지 않는다.Referring to FIGS. 9A and 9B, the PRBs (1, 2? N) constitute the desired BW 915. If the number of eigenvalues detected in PRB1 920 is one (

), The subspace BIS BW is PRB (0, -1,

), ≪ / RTI > Extension 905 continues to be performed until a unique value is not detected in one PRB, such as 900 in FIG. 9A. Alternatively, if the number of eigenvalues detected in PRB1 920 is 0

), The subspace BIS BW does not extend to the left, as shown at 910 of FIG. 9B.

In one embodiment, expansion to the right may also be performed similar to extension 905 to the left. In another embodiment, such an extension may be combined with a subspace BIS operation which is the next step of the proposed algorithm.

Figure 10 is a flow diagram that extends the PRB in the subspace BIS algorithm according to various embodiments of the present invention. The embodiment shown in Fig. 10 is only for explaining the present invention, and does not limit the scope of the present invention. Flowchart 1000 illustrates a sequential series of steps, but may be performed sequentially, rather than concurrently or overlapping, with a particular sequence of operations, steps, or steps, unless explicitly stated otherwise, No inference can be drawn from the step with respect to performing the steps exclusively described without the occurrence of the step. 10 may be implemented by a processor (e.g., the main processor 340 of the UE or the processor 378 of the BS).

로 초기화된다. 블록 1010에서, 에너지

는 PRB i에서 감지된다. 블록 1015에서, PRB i에 대하여, PRB i에서 수신된 신호의 분산 행렬의 고유값을 기반으로 하는 에너지

는 기준값과 비교된다. 블록 1020에서, i가 1을 초과하는지 결정된다. 만약에,

가 기준값을 초과하고 i가 1을 초과하면, 블록 1025에서, 확대가 수행된다. 이러한 프로세스는 블록 1030으로 진행할 때까지 계속된다.As shown, to determine the subspace BIS BW, the processor may extend by one PRB from the leftmost PRB of the desired BW to the left of each iteration. In block 1005, i is

. At block 1010,

Is detected at PRB i. At block 1015, for PRB i, the energy based on the eigenvalues of the variance matrix of the received signal at PRB i

Is compared with the reference value. In block 1020, it is determined if i exceeds one. If the,

Lt; / RTI > exceeds the reference value and i exceeds 1, then at block 1025, magnification is performed. This process continues until block 1030 is reached.

로 초기화된다. 블록 1010에서, 에너지

는 PRB io에서 감지된다. 블록 1015에서, PRB i에 대하여, PRB i에서 수신된 신호의 분산 행렬의 고유값을 기반으로 하는 에너지

는 기준값과 비교된다. 블록 1020에서, i가 1을 초과하는지 결정된다. 만약에,

가 기준값을 초과하고 i가 1을 초과하면, 블록 1025에서, 오른쪽으로 확장이 수행된다. 이러한 프로세스는 블록 1030으로 진행할 때까지 계속된다.Similarly, the subspace BIS BW may be extended by one PRB from the rightmost PRB of the desired BW to the right of every iteration. In block 1005, i is

. At block 1010,

Is detected in the PRB io. At block 1015, for PRB i, the energy based on the eigenvalues of the variance matrix of the received signal at PRB i

Is compared with the reference value. In block 1020, it is determined if i exceeds one. If the,

Lt; / RTI > exceeds the reference value and i exceeds 1, expansion is performed to the right in block 1025. This process continues until block 1030 is reached.

에 대한 간섭 케이스 검출을 다음과 같은 단계에 따라 수행한다. A subspace BIS block (e.g., via the BIS algorithm) may be used to determine two consecutive RBs in the estimated subspace BIS BW

The interference case detection is performed according to the following steps.

(1) The number of interferers is detected in RB k and k + 1.

에서 출발하는 간섭자의 개수, 도착하는 간섭자의 개수, 계속 중인 간섭자의 개수를 검출한다.(2) RB pair

The number of arriving interferers, and the number of interferers in progress.

In step (1), the subspace BIS block detects the number of interferers in each RB using the eigenvalues of the covariance matrix of the received signal (the signal from which the desired signal is removed).

The covariance matrix of RB k is given by Equation 1 below.

는 RB k에서 수신된 샘플의 집합이고,

는 RB k에서의 자원 요소(resource element, RE) m에 대응하는 수신 신호 벡터(vector)이다. 그리고

와

는 원하는 신호 벡터와 원하는 신호 벡터에 대한 공분산 행렬이다.

와

는

번째 간섭 신호 벡터와

번째 간섭 신호 벡터에 대한 공분산 행렬이다.

은 간섭자의 개수이고,

은 잡음 분산이다.here,

Is the set of samples received at RB k,

Is a received signal vector corresponding to a resource element (RE) m at RB k. And

Wow

Is a covariance matrix for a desired signal vector and a desired signal vector.

Wow

The

Th interference signal vector

Is the covariance matrix for the ith interfering signal vector.

Is the number of interferers,

Is the noise variance.

Assuming that the desired signal can be perfectly removed from the received signal, the covariance matrix without the desired signal at RB k is given by Equation 2 below.

는 고유값 분해(eigenvalue decomposition)를 나타내며, 다음의 수학식 3과 같다.here,

Represents an eigenvalue decomposition, and is expressed by Equation 3 below.

는 간섭 신호 부분 공간을 나타내며,

는 잡음 부분 공간을 나타낸다.

의 고유값들은 RB k에서의 간섭자의 개수를 결정하는데 사용된다.

는 RB k에서의 간섭자의 개수를 표시하기 위해 사용된다.here,

Represents an interfering signal subspace,

Represents the noise subspace.

Are used to determine the number of interferers at RB k.

Is used to indicate the number of interferers at RB k.

과

의 신호 공간의 차원(dimension) 또는 계수(rank)를 이용한다.In step (2), the subspace BIS block computes the total number of interferers at RB k and k + 1 using the eigenvalues of the covariance matrix of the signals received at RB k and k + 1 Lt; RTI ID = 0.0 >

and

The size or rank of the signal space of the signal.

The mean of the covariance matrix of the two RBs is defined as: < RTI ID = 0.0 >

의 고유값 분해가 수행된다.

의 고유값들은 함께 결합된

와

의 신호 공간의 차원 또는 계수를 결정하기 위해 사용된다.

는

의 고유값들을 나타낸다. 어떤 실시 예에서는, 변수

는 RB K=1에서 후보 간섭 BW의 시작, RB k에서의 후보 간섭 BW의 끝, 연속하는 RB들

에서 이어지는 후보 간섭 BW를 포함하는 다수의 이벤트를 나타낸다. 그러므로

및

과 함께 변수

는 다음과 같은 세 가지의 가능성을 구분한다. 세 가지 가능성은 PRB k+1에서의 후보 간섭 BW의 시작, PRB k에서의 후보 간섭 BW의 끝 및 PRB

에서의 이어지는 후보 간섭 BW를 포함한다.And

Is performed.

The eigenvalues of < RTI ID = 0.0 &

Wow

Is used to determine the dimension or modulus of the signal space of the signal.

The

≪ / RTI > In some embodiments,

The start of candidate interference BW at RB K = 1, the end of candidate interference BW at RB k,

Lt; RTI ID = 0.0 > BW. ≪ / RTI > therefore

And

With variable

It distinguishes three possibilities as follows. The three possibilities are the start of the candidate interference BW at PRB k + 1, the end of the candidate interference BW at PRB k,

Lt; RTI ID = 0.0 > BW < / RTI >

11A and 11B are diagrams for detecting an interference case in various embodiments of the present invention. The embodiments shown in Figs. 11A and 11B are merely illustrative of the present invention, and do not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

에 대해 검출된 값은 유효한 간섭 케이스를 결정하기 위해 사용된다. 예를 들어, 만약에,

인 경우, 도 11a의 1100과 같이, 기지국은 RB k와 k+1에서 1개의 간섭 사용자(IUE1)를 가질 수 있다. 다른 예로, 만약에,

인 경우, 도 11b의 1110과 같이, 기지국은 RB k에서 하나의 간섭 사용자(IUE1)를, RB k+1에서 다른 간섭 사용자(IUE2)를 가질 수 있다.

값에 따른 유효한 간섭 케이스는 도 22a 내지 22d에 자세히 도시되어 있다.Referring to Figures 11A and 11B,

Is used to determine a valid interference case. For example, if,

, The base station may have one interference user IUE1 at RB k and k + 1, as in 1100 of FIG. 11A. As another example, if,

, The base station may have one interference user IUE1 in RB k and another interference user IUE2 in RB k + 1, as in 1110 of FIG. 11B.

The valid interference cases according to the values are shown in detail in Figures 22a to 22d.

에 대해 검출된 값은 수신 신호의 공분산 행렬의 고유값에 대한 기준값 테스트를 기반으로 하여 획득될 수 있다. 수신 신호의 공분산 행렬의 고유값 행렬은 다음의 수학식 5와 같다.According to one embodiment,

May be obtained based on a reference value test for the eigenvalue of the covariance matrix of the received signal. The eigenvalue matrix of the covariance matrix of the received signal is expressed by Equation (5).

는 획득된 간섭 대 잡음 비(Interference to Noise Power Ratio, INR)를 나타내며,

는 획득된 INR의 함수를 나타낸다.here,

Denotes an obtained interference-to-noise power ratio (INR)

Represents the function of the obtained INR.

The reference value test is as shown in Equation (6).

의 함수인

로 나타낼 수 있다.Here, T represents a reference value, and for example, a target INR in dB,

Function of

.

,

,

에 대한 기준값은 동일할 수 있다. 다른 실시 예에서, 기준값은 다를 수 있다. 또 다른 실시 예에서, 기준값은 고유값의 함수일 수 있다. 또 다른 실시 예에서, 기준값은 서로 다른 고유값들에 대해 다를 수 있다. 예를 들면, 최대 고유값에 대한 기준값은 최대값일수 있고, 두 번째 고유값에 대한 기준값은 최대 고유값에 대한 기준값보다 낮을 수 있다. 어떤 실시 예에서는, 기준값은 수학식 7과 같이, 하한과 상한 사이의 값으로 선택될 수 있다:In one embodiment,

,

,

The reference value may be the same. In another embodiment, the reference value may be different. In yet another embodiment, the reference value may be a function of the eigenvalue. In yet another embodiment, the reference value may be different for different eigenvalues. For example, the reference value for the maximum eigenvalue may be a maximum value, and the reference value for the second eigenvalue may be lower than the reference value for the maximum eigenvalue. In some embodiments, the reference value can be selected as a value between the lower and upper limits, as shown in equation (7): < EMI ID =

의 검출된 값은 수신 신호의 공분산 행렬의 몇 개(전부가 아닌)의 우성(dominant) 고유값에 대한 기준값 테스트를 기반으로 하여 획득될 수 있다. 예를 들면, 먼저, 모든 고유값들이 분류되고, 그 이후에 최대의 고유값부터 기준값 테스트가 수행될 수 있다. 예를 들면, 기준값 테스트는 간섭 전력 합(sum interference power)의 목표 퍼센트가 검출될 때까지 순서에 따라 반복될 수 있다.In one embodiment,

May be obtained based on a reference value test for dominant eigenvalues of some (but not all) covariance matrices of the received signal. For example, first, all the eigenvalues are classified, and then the reference value test can be performed from the maximum eigenvalue. For example, the reference value test may be repeated in order until a target percentage of the sum interference power is detected.

에 대한 기준값 테스트가 수행될 수 있다. According to one embodiment, according to the algorithm described in Table 1

Can be performed.

For

Upper bound:

(Ex:

)
Lower bound:

(Ex:

)
Choose a suitable threshold: T (Ex:

If

(Threshold test)
Include

in set

I
If

(Stop if target % of sum interference power is reached)
Break;
End if
Else
Break; (Stop if eigenvalue i fails threshold test)
End if
End For
Number of detected eigenvalues = size of set I.Initialization:

For

Upper bound:

(Ex:

)
Lower bound:

(Ex:

)
Choose a suitable threshold: T (Ex:

If

(Threshold test)
Include

in set

I
If

(Stop if target% of sum interference power is reached)
Break;
End if
Else
Break; (Stop if eigenvalue i fails threshold test)
End if
End For
Number of detected eigenvalues = size of set I.

는 내림차순으로 분류된 고유값들을 나타내고,

은 고유값의 개수를 나타낸다.

은 목표 dB 단위의 INR을 나타내고,

는 간섭 전력 합의 목표 퍼센트를 나타낸다.here,

Represents eigenvalues classified in descending order,

Represents the number of eigenvalues.

Represents the INR in the target dB unit,

Represents the target percentage of the interference power sum.

은 원하는 신호 제거 후의 수신 신호의 평균 공분산의 최소 고유값을 이용하여 추정될 수 있다. 만약에, 우성 간섭자의 개수가 수신 안테나 또는 고유값의 개수 미만인 경우, 이러한 실시 예는 바람직할 수 있다.In some embodiments, the noise variance

Can be estimated using the minimum eigenvalue of the mean covariance of the received signal after the desired signal cancellation. If the number of dominant interferers is less than the number of receive antennas or eigenvalues, then this embodiment may be preferred.

의 추정값은 특정 PRB에서의 최소 고유값과 동일할 수 있다. 어떤 실시 예에서,

의 추정값은 원하는 사용자 PRB 할당을 통한 최소 고유값들의 평균에 의해 획득될 수 있다 (예를 들면,

,

는 원하는 사용자 PRB의 개수를 나타내고,

는 PRB i에 대한 최소 고유값을 나타냄.). 어떤 실시 예에서,

의 추정값은 부분 공간 BIS BW를 통한 최소 고유값들을 평균함으로써 획득될 수 있다.In some embodiments,

May be equal to the minimum eigenvalue in a particular PRB. In some embodiments,

May be obtained by an average of the minimum eigenvalues through the desired user PRB allocation (e.g.,

,

Represents the number of desired user PRBs,

Represents the minimum eigenvalue for PRB i). In some embodiments,

Can be obtained by averaging the minimum eigenvalues over the subspace BIS BW.

의 감지된 값은 데이터(원하는 신호 제거 후의 수신 신호)에 맞는 모델 선택을 기반으로 하여 획득될 수 있다.In some embodiments,

May be obtained based on the model selection corresponding to the data (the received signal after the desired signal cancellation).

의 검출된 값은 수학식 8이 최소가 되는,

의 값이 될 수 있다. The model selection based on the maximum aposterori probability is introduced by M. Wax and T. Kailath in "Detection of Signals by Information Theoretic Criteria" (IEEE Trans. Acoust. Assuming that a sample of zero mean is input to the iid complex Gaussian,

Lt; RTI ID = 0.0 > (8) < / RTI &

≪ / RTI >

Here, p denotes the number of receive (Rx) antennas, l _i denotes an i-th eigenvalue of a covariance matrix arranged in descending order, and N denotes the number of received samples.

In some embodiments, the subspace BIS block performs interference case detection for all pairs of consecutive RBs in the estimated subspace BIS BW, and detects the start and end of the interferer BW detected through the entire subspace BIS BW, and may provide a set of candidate interference BWs.

12 is a diagram for determining a set of subspace interference BWs according to a first embodiment of the present invention. The embodiment shown in Fig. 12 is only for explaining the present invention, and does not limit the scope of the present invention. That is, other embodiments may be used within the scope of the present invention.

는 원하는 RB들이고, RB

와

은 좌측과 우측 확장이다. 획득된 간섭 BW들의 집합 1200은 5개의 후보를 가진다.Referring to FIG. 12,

Are the desired RBs, and RB

Wow

Are left and right extensions. The set of acquired interference BWs 1200 has five candidates.

은 고유값 (15.1, 3.2, 1.5)로부터 결정되고,

는 고유값 (12.3, 2.9, 1.3)로부터 결정되고,

은 고유값 (8.9, 1.1, 0.9)로부터 결정되고,

은 고유값 (6.6, 0.96, 0.9)로부터 결정되고,

은 고유값 (9.6, 3.2, 1.2)로부터 결정되고,

은 고유값 (11.3, 2.9, 1.3)로부터 결정된다. 그리고

은 고유값 (13.7, 3.05, 1.4)로부터 결정되고,

은 고유값 (10.6, 2.1, 1.1)로부터 결정되고,

은 고유값 (7.75, 1.03, 0.9)로부터 결정되고,

은 고유값 (8.1, 2.08, 1.05)로부터 결정되고,

은 고유값 (10.45, 3.05, 1.25)로부터 결정된다. 부분 공간 BIS BW에서 연속하는 PRB들 (k,k+1)의 모든 쌍에 대해,

검출에 대한 고유값들은 기준값(예: 2)과 비교된다.13 is a diagram for determining a set of subspace interference BWs according to a second embodiment of the present invention. According to the method 1300 for determining the set of subspace interference BWs shown in FIG. 13,

Is determined from the eigenvalues (15.1, 3.2, 1.5)

Is determined from the eigenvalues (12.3, 2.9, 1.3)

Is determined from the eigenvalues (8.9, 1.1, 0.9)

Is determined from the eigenvalues (6.6, 0.96, 0.9)

Is determined from the eigenvalues (9.6, 3.2, 1.2)

Is determined from the eigenvalues (11.3, 2.9, 1.3). And

Is determined from the eigenvalues (13.7, 3.05, 1.4)

Is determined from the eigenvalues (10.6, 2.1, 1.1)

Is determined from the eigenvalues (7.75, 1.03, 0.9)

Is determined from the eigenvalues (8.1, 2.08, 1.05)

Is determined from the eigenvalues (10.45, 3.05, 1.25). For every pair of consecutive PRBs (k, k + 1) in subspace BIS BW,

The eigenvalues for detection are compared to a reference value (e.g., 2).

의 고유값 3개 중에서 2개가 기준값을 초과하므로,

에 대한 간섭자의 개수는 2로 결정되고,

의 고유값 3개 중에서 2개가 기준값을 초과하므로,

에 대한 간섭자의 개수는 2개로 결정되고,

의 고유값 3개 중에서 2개가 기준값을 초과하므로,

에 대한 간섭자의 개수는 2개로 결정될 수 있다. 즉, (

,

,

)에 대한 간섭자의 개수는 (2, 2, 2)로 결정될 수 있다.For example,

Two of the eigenvalues of 3 < RTI ID = 0.0 >

The number of interferers is determined to be 2,

Two of the eigenvalues of 3 < RTI ID = 0.0 >

Lt; / RTI > is determined to be two,

Two of the eigenvalues of 3 < RTI ID = 0.0 >

The number of interferers to be used can be determined to be two. In other words, (

,

,

) Can be determined to be (2, 2, 2).

) 의 5 개의 검출된 값들((2, 2, 2), (2, 1, 2), (1, 1, 1), (1, 2, 2), (2, 2, 2))은 5개의 간섭 케이스들에 맵핑(mapping)된다. 이러한 간섭 케이스들의 병합은 3개의 후보 간섭 BW들((1, 2, 3, 4, 5, 6), (1, 2), (5, 6))을 생성한다.After that, (

(2, 2, 2), (1, 1, 1), (1, 2, 2), (2, 2, 2) Mapped to interference cases. The merging of these interference cases produces three candidate interference BWs ((1,2,3,4,5,6), (1,2), (5,6).

이 간섭 케이스와 맵핑되면, 부분 공간 BIS BW에서 연속하는 RB들의 몇몇 쌍들에 대한 간섭 케이스 검출의 개선이 필요한 경우가 있을 수 있다. 이하에서, 개선에 대한 3가지 실시 예를 설명하고자 한다. 다른 가능한 개선들도 알고리즘에 유사하게 포함될 수 있다.The detected values

When mapped to this interference case, it may be necessary to improve the interference case detection for some pairs of consecutive RBs in the subspace BIS BW. In the following, three embodiments for improvement are described. Other possible improvements may similarly be included in the algorithm.

의 값이 유효한 간섭 케이스에 맵핑되지 않는 경우, 다음과 같은 옵션(option)들 중 하나에 따라

의 동일한 값을 가지는 유효한 간섭 케이스 중 하나에 맵핑될 수 있다. 옵션 A-1에서는, 모든 유효한 간섭 케이스들은 같은 확률로 일어난다는 가정하에 맵핑이 무작위(random)로 이루어진다. 옵션 B-1에서는, 맵핑은 유효한 간섭의 케이스들에 대한 사전 지식을 기반으로 이루어진다. 옵션 C-1에서는, 가장 가까운

값을 가지는 유효한 간섭 케이스에 맵핑된다.14A is a diagram illustrating an invalid case mapping in accordance with various embodiments of the present invention. If the,

Is not mapped to a valid interfering case, then the value of < RTI ID = 0.0 >

Lt; RTI ID = 0.0 > 1 < / RTI > In option A-1, the mapping is random, assuming that all valid interference cases occur with the same probability. In option B-1, the mapping is based on prior knowledge of valid cases of interference. In option C-1,

0.0 > interference < / RTI >

는 유효한 간섭 케이스인

또는

중 어느 것에도 맵핑될 수 없다. 옵션 A-1에 따르면, 검출된 값

는

또는

에 무작위로 맵핑된다. 옵션 B-1에 따르면, 검출된 값

는 사전 지식을 기반으로 더 높은 확률을 갖는 쪽으로 맵핑된다. 옵션 C-1에 따르면, 검출된 값

는

에 맵핑되는데, 이는 가장 가까운

값을 가지기 때문이다.For example, as in 1400 of Fig. 14A,

Is a valid interference case

or

Can not be mapped to any of them. According to option A-1, the detected value

The

or

. ≪ / RTI > According to Option B-1, the detected value

Is mapped to a higher probability based on prior knowledge. According to Option C-1, the detected value

The

Lt; RTI ID = 0.0 > closest

Value.

의 값이 한 간섭자가 RB k+1에서 출발하며 RB k에 하나 이상의 간섭자가 존재하는 것에 해당하는 경우라면, RB k+1에서 간섭 BW가 계속되거나 끝날지에 대한 결정이 다음의 옵션들 중 하나에 따라 이루어진다. 옵션 A-2에 따르면, 모든 간섭 BW에 대한 확률이 같다는 가정하에 결정은 랜덤이다. 옵션 B-2에 따르면, 간섭 BW에 대한 사전지식을 기반으로 이루어진다. 옵션 C-2에 따르면, 복수의 간섭 BW 추측들은, 각 추측마다 검출된 간섭자들의 개수가 출발할 수 있도록, 다음 단계를 위해 생성된다. 옵션 D-2에 따르면, 결정은 k보다 앞선 RB에서 획득된 고유값을 기반으로 하여 이루어진다.14B is a diagram illustrating a continuous BW decision according to various embodiments of the present invention. If the

, The decision as to whether the interfering BW will continue or end at RB k + 1 will be made by one of the following options, if one interferer starts at RB k + 1 and corresponds to the presence of one or more interferers in RB k . According to option A-2, the decision is random, assuming that the probabilities for all interference BW are the same. According to option B-2, it is based on prior knowledge of interference BW. According to option C-2, a plurality of interfering BW guesses are generated for the next step, so that the number of interferers detected for each guess can start. According to option D-2, the decision is made on the basis of the eigenvalues obtained in RBs ahead of k.

로 검출되는 경우, 결정은 RB k+1에서 출발하는 두 간섭자들(예: IUE1, IUE2)과 관련되어 생성될 필요가 있다. 옵션 A-2에 따르면, 결정은 두 간섭자가 출발할 확률이 동일하다고 가정하에 랜덤하게 이루어진다. 옵션 B-2에 따르면, 결정은 사전 지식의 추정으로 랜덤하게 이루어진다. 옵션 C-2에 따르면, 도 14b의 1410과 같이, 두 개의 간섭 BW 추측이 알고리즘의 다음 단계를 위해 생성된다. For example,

, The decision needs to be made in relation to the two interferers (e.g., IUE1, IUE2) starting at RB k + 1. According to option A-2, the decision is made randomly assuming that the two interferers have the same starting probability. According to option B-2, the decision is made randomly with an estimation of prior knowledge. According to option C-2, two interference BW guesses are generated for the next step of the algorithm, as at 1410 in FIG. 14B.

의 값이 모든 간섭자들이 RB k+1에서 출발하는 것으로 검출된 것에 해당한다면, 이러한 케이스들은 실제로 일어날 가능성이 낮고 이후의 단계에서 심각한 검출 에러가 발생할 수 있기 때문에 다른 유효한 케이스에 맵핑되거나 복수의 추측을 생성한다. 옵션 A-3에서, 이러한 케이스는 하나의 간섭자가 출발하지 않는 유효한 케이스에 맵핑된다. 예를 들면,

를

에 맵핑할 수 있다. 옵션 B-3에서, 사전 지식을 기반으로 하여 유효한 케이스에 맵핑될 수 있다. 옵션 C-2에서, 복수의 추측들이 다음 단계에서 생성된다. 예를 들면,

를 가 유지될 수 있다.14C is a diagram illustrating all interferor departure mapping in accordance with various embodiments of the present invention. If the,

Is mapped to another valid case or if there are multiple guesses, such as the case where all of the interferers are detected to be starting at RB k + 1, then these cases are less likely to occur and serious detection errors may occur in subsequent steps . In option A-3, this case is mapped to a valid case where one interferer does not start. For example,

To

. ≪ / RTI > In Option B-3, it can be mapped to a valid case based on prior knowledge. In option C-2, multiple guesses are generated in the next step. For example,

To Can be maintained.

이 감지된 경우, 두 간섭자(예: IUE1, IUE2) 모두 RB k+1에서 출발할 수 있다. 이러한 경우가 감지되면, 옵션 A-3에 따라

에 맵핑될 수 있다. 옵션 B-3에서 사전 지식을 기반으로 하여, 유효한 케이스(예:

)에 맵핑되거나 옵션 C-3에서 두 가지 추측

을 생성할 수 있다.For example, as shown at 1420 in Fig. 14C,

, Both interferers (eg, IUE1, IUE2) can start at RB k + 1. If this is detected, follow option A-3

Lt; / RTI > Based on prior knowledge in Option B-3, a valid case (eg,

) Or two guesses in option C-3

Can be generated.

(2, 1, 1), (1, 2, 1), (1, 2, 1), (1, 2, 1), (2, 1, 1) 및 (1, 2, 1)인 6가지의 무효한 케이스 맵핑 (이슈 1),

(2, 1, 2), (2, 1, 2), (2, 1, 2), 및 (2, 1, 2)인 4 가지의 연속하는 BW 결정 (이슈 2) 및

(1, 1, 2)인 모든 간섭자 중 하나의 출발 (이슈 3)를 포함한다. Figure 15 is a snapshot of an algorithm reflecting three issues according to the options C-1, C-2, and C-3 according to various embodiments of the present invention. The snapshot 1500 shown in FIG. 15 includes the following issues. Here,

(1, 2, 1), (1, 2, 1), (1, 2, 1) Invalid Case Mapping (Issue 1),

Four consecutive BW determinations (Issue 2) with (2, 1, 2), (2, 1, 2), (2, 1, 2)

(Issue 3) of all interferers that are (1, 1, 2).

의 값은 (2,1,2), (1, 2, 2), (1, 2, 2), (1, 2, 2), (2, 1, 2), (1, 2, 2)에 각각 맵핑될 수 있다. 다른 실시 예에 따르면, 옵션 C-2가 이슈 2를 다루기 위해 적용되고 옵션 C-3가 이슈 3에 적용될 수 있다. 이때,

= 32개의 추측이 생성된다. 이에 따라, 32개의 간섭 추측이 있고, 그 중에서 하나(top hypothesis)가 정확한 간섭 BW를 포함한다.According to one embodiment, Option C-1 may be applied to handle Issue 1,

(1, 2, 2), (1, 2, 2), (2, 1, 2), (1, 2, 2) Respectively. According to another embodiment, option C-2 may be applied to issue 2 and option C-3 may be applied to issue 3. [ At this time,

= 32 speculations are generated. Thus, there are 32 interference hypotheses, one of which (top hypothesis) contains the correct interference BW.

의 최대값 또는 간섭 계층의 최대 개수)을 가질 수 있다. 예를 들면, 도면 16의 1600에는, 최대

과 최대

에 대한 알고리즘의 두 가지 사례가 도시되어 있다.16 is a diagram illustrating two variations of an algorithm according to various embodiments of the present invention. Candidate interference hypotheses may be used to determine a plurality of interfering BW candidates (e.g.,

Or the maximum number of interference layers). For example, in 1600 of FIG. 16,

And max

Two examples of algorithms for < RTI ID = 0.0 >

(계층의 개수)의 값을 기반으로 한다. 예를 들면, 최대

에 대한 복잡도는 최대

에 대한 것보다 작을 것이다. 그러나 BIS 부분 공간의 크기는 최대

보다 최대

이 더 크기 때문에, 최대

인 부분 공간 BIS 알고리즘의 성능은 최대

보다 좋다. 그 이유는 일반적으로 BIS 부분 공간의 크기가 클수록 성능도 향상되기 때문이다.The algorithm complexity is maximum

(The number of layers). For example,

The complexity for

Lt; / RTI > However, the size of BIS subspace is maximum

Maximum

Because of its larger size,

The performance of the subspace BIS algorithm is maximized

It is better. This is because the larger the BIS subspace, the better the performance.

17 is a flow chart of the DMRS algorithm according to various embodiments of the present invention. The embodiment shown in Fig. 17 is only for explaining the present invention, and does not limit the scope of the present invention. Flowchart 1700 illustrates a sequence of sequential steps, but may be performed sequentially, rather than concurrently or overlapping, with a particular sequence of operations, steps, or steps, unless explicitly stated otherwise, No inference can be drawn from the step with respect to performing the steps exclusively described without the occurrence of the step. The procedure shown in Fig. 17 may be implemented by a processor (e. G., The main processor 340 of the UE or the processor 378 of the BS).

)와 모든 가능한 DMRS 시퀀스들

의 교차-상관 관계(cross-correlation)를 기반으로 수행될 수 있다. 예를 들면, 모든 가능한 DMRS 시퀀스들은 다음과 같은 조건을 만족할 수 있다.

, 인접한 셀의 모든

의 집합;

, 순환 시프트(cyclic shift);

, 크기;

,

; 및

는 부분 공간 BIS 블록으로부터의 후보 간섭 BW.As shown in FIG. 17, the base station (e.g., BS2 102) performs the DMRS BIS using the obtained candidate interference BWs. The DMRS search space is configured at block 1705. At block 1710, the candidate DMRS estimates of the interferers are received signal

) And all possible DMRS sequences

Based on the cross-correlation of < / RTI > For example, all possible DMRS sequences may satisfy the following conditions.

, All of the adjacent cells

A set of;

, Cyclic shift;

, size;

,

; And

Is the candidate interference BW from the subspace BIS block.

= 1)에서 수행된 것이고 전체 DMRS 탐색과 비교된 것이다. 시뮬레이션 환경과 관련된 정보는 다음과 같다: 10M Hz BW (50 RBs); 완벽하게 겹쳐진 원하는 BW와 간섭 BW; Ped. B 채널과 AWGN; SNR은 0dB; u와

는 랜덤; 표 2에 포함된 3가지 간섭 케이스.The simulation results below are for the subspace BIS algorithm. The result is one interference layer (maximum

= 1) and compared with the full DMRS search. Information related to the simulation environment is as follows: 10 M Hz BW (50 RBs); Perfectly overlapped desired BW and interference BW; Ped. B channel and AWGN; SNR is 0 dB; u and

Is random; Three interference cases included in Table 2.

Case 1 (36 RBs) Case 2 (25 RBs) Case 3 (12 RBs) INR (dB) MSC INR (dB) MSC INR (dB) MSC Desired UE - 8 - 10 - 12 Interference # 1 8.3 10 7.2 12 4.6 13 Interference # 2 2.3 9 0.2 9 -5.8 14 Interference -1.6 8 -4.8 10 -14 12

18 is a graph illustrating the reduction of the DMRS search space in accordance with various embodiments of the present invention. Referring to FIG. 18, a reduction in the large search space (> 184 times) is achieved with the proposed partial space algorithm over the entire DMRS search space. Further, as shown in Fig. 19, the correct interference BW is always included in the reduced subspace with a probability close to unity. 20 is a graph illustrating the detection probabilities of three DMRS sequences corresponding to three interferers in accordance with various embodiments of the present invention. Referring to FIG. 20, at least two interfering DMRS sequences corresponding to two dominant interferers are detected with a high probability of 0.85 or more.

의 간섭자들이 존재하고, (2) 수신기의 안테나 개수는 네 개(

)라고 가정한다. 전체 공간 {

}은 유효한 간섭 케이스들과 무효한 간섭 케이스들을 모두 포함한다. 유효한 간섭 케이스들은

값들이 아래의 조건을 만족하는 것에 해당한다. 여기서, 조건은,

과

이다. 무효한(또는 불가능한) 케이스들은 물리적으로 불가능한 다른 모든 케이스를 의미한다.For example, valid interference cases and invalid interference cases can be specified and stored in advance. (1) Maximum per PRB

(2) the number of antennas of the receiver is four

). Total space {

} Includes both valid and invalid interference cases. Valid interference cases

The values correspond to the following conditions. Here,

and

to be. Invalid (or impossible) cases mean all other cases that are physically impossible.

의 쌍에 대한 간섭 케이스 검출이 수행되면, 그 결과를 기반으로, 간섭 케이스가 물리적으로 유효한 케이스인지 무효한 케이스인지 검출될 수 있다. 도 21의 2100을 참조하면, 사선으로 유효한 케이스를 도시하고 있으며, 무사선으로 무효한 케이스를 도시하고 있다.If the consecutive RBs

It is possible to detect whether the interference case is a physically valid case or an invalid case based on the result of the detection of the interference case. 21, reference numeral 2100 denotes a case which is valid as an oblique line and shows a case which is invalid as a non-defective line.

FIGS. 22A through 22D are diagrams illustrating a map index tuple corresponding to a valid interference case according to an embodiment of the present invention. FIG.

인 4 개의 튜플(tuple)들을 유효한 간섭 케이스에 맵핑하는 것을 도시하고 있다. 도 22a를 참조하면, 다음과 같은 맵핑이 정의된다.

의 인덱스 튜플은 RB들 k와 k+1에서 간섭이 없는 간섭 시나리오(scenario)에 맵핑된다.

의 인덱스 튜플은 RB k에서 간섭 UE가 0개이고 RB k+1에서 간섭 UE가 1개인 간섭 시나리오에 맵핑된다.

의 인덱스 튜플은 RB k에서 간섭 UE가 0개이고 RB k+1에서 간섭 UE가 2개인 간섭 시나리오에 맵핑된다.

의 인덱스 튜플은 RB k에서 간섭 UE가 0개이고 RB k+1에서 간섭 UE가 3개인 간섭 시나리오에 맵핑된다. 다른 도면의 맵핑도 비슷하게 정의된다.For example, FIG. 22A illustrates an example

Lt; RTI ID = 0.0 > 4 < / RTI > tuples to a valid interference case. Referring to FIG. 22A, the following mapping is defined.

≪ / RTI > is mapped to an interference-free scenario in RBs k and k + 1.

Is mapped to an interference scenario with one interfering UE at RB k and one interfering UE at RB k + 1.

Is mapped to an interference scenario where there are 0 interfering UEs in RB k and 2 interfering UEs in RB k + 1.

Is mapped to an interference scenario in which there are 0 interfering UEs in RB k and 3 interfering UEs in RB k + 1. The mapping of other drawings is similarly defined.

인 유효한 간섭 케이스들을 도시하고 있으며, 도 22b는

인 유효한 간섭 케이스들을 도시하고 있다. 도 22c는

인 유효한 간섭 케이스들을 도시하고 있고, 도 22d는

인 유효한 간섭 케이스들을 도시하고 있다.22A is a cross-

Lt; RTI ID = 0.0 > 22B < / RTI >

Lt; / RTI > Figure 22c

Lt; RTI ID = 0.0 > 22d < / RTI >

Lt; / RTI >

As used in this document, the term "module" may refer to a unit comprising, for example, one or a combination of two or more of hardware, software or firmware. A "module" may be interchangeably used with terms such as, for example, unit, logic, logical block, component, or circuit. A "module" may be a minimum unit or a portion of an integrally constructed component. A "module" may be a minimum unit or a portion thereof that performs one or more functions. "Modules" may be implemented either mechanically or electronically. For example, a "module" may be an application-specific integrated circuit (ASIC) chip, field-programmable gate arrays (FPGAs) or programmable-logic devices And may include at least one.

At least a portion of a device (e.g., modules or functions thereof) or a method (e.g., operations) according to various embodiments may include, for example, computer-readable storage media in the form of program modules, As shown in FIG. When the instruction is executed by a processor (e.g., processor 110), the one or more processors may perform a function corresponding to the instruction. The computer readable storage medium may be, for example, memory 130. [

The computer readable recording medium may be a hard disk, a floppy disk, a magnetic media (e.g., a magnetic tape), an optical media (e.g., a compact disc read only memory (CD-ROM) digital versatile discs, magneto-optical media such as floptical disks, hardware devices such as read only memory (ROM), random access memory (RAM) Etc. The program instructions may also include machine language code such as those produced by a compiler, as well as high-level language code that may be executed by a computer using an interpreter, etc. The above- May be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

Modules or program modules according to various embodiments may include at least one or more of the elements described above, some of which may be omitted, or may further include additional other elements. Operations performed by modules, program modules, or other components in accordance with various embodiments may be performed in a sequential, parallel, iterative, or heuristic manner. Also, some operations may be performed in a different order, omitted, or other operations may be added. And the embodiments disclosed in this document are presented for the purpose of explanation and understanding of the disclosed technology and do not limit the scope of the technology described in this document. Accordingly, the scope of this document should be interpreted to include all modifications based on the technical idea of this document or various other embodiments.

Claims (20)

A method of operating a network device in a wireless communication system,
Removing a target signal of a target bandwidth (BW) from a received signal;
Estimating a parameter related to interference based on the received signal from which the target signal is removed;
Estimating an interference signal based on the interference-related parameter;
And removing the interference signal from the received signal.
The method according to claim 1,
Wherein the step of removing the target signal of the target bandwidth (BW) comprises the step of removing the target signal from the received signal if decoding of the received signal fails.
The method according to claim 1,
Decoding the received signal from which the interference signal has been removed,
And estimating the interference-related parameter based on the received signal from which the interference signal is removed if the decoding fails.
2. The method of claim 1, wherein estimating the parameter associated with the interference comprises:
Determining blind interference sensing (BIS) BW by extending the target BW based on energy for each of the resource blocks (RBs)
Determining at least one candidate interference BW based on the number of interferers for each of the RBs of the subspace BIS BW;
And determining at least one interference and demodulation reference signal (DMRS) sequence by performing DMRS detection on the candidate interference BW.
5. The method of claim 4, wherein the determining of the partial space BIS BW comprises:
Detecting energy for at least one RB before the start RB and the end RB of the target BW;
Determining the subspace BIS BW by adding the at least one RB to the target BW based on a comparison result between the energy and a predetermined reference value.
5. The method of claim 4, wherein the step of determining the candidate interference BW comprises:
Determining at least one first eigenvalue, at least one second eigenvalue, and at least one third eigenvalue for a pair of RBs for consecutive RBs in the subspace BIS BW;
Determining a number of interferers for each of the RBs and a number of interferers for the pair of BSs based on a result of comparison between the first to third eigenvalues and a predetermined reference value;
Determining the candidate interference BW based on the number of interferers for each of the RBs and the number of interferers for the pair of BSs.
The method according to claim 6,
Wherein the first and second eigenvalues are determined based on covariance matrices for the consecutive RBs and the third eigenvalue is determined based on a common covariance matrix for the consecutive RBs.
7. The method of claim 6, wherein the step of determining the candidate interference BW comprises:
Mapping the number of interferers to consecutive RBs in the candidate interference BW to an interference case;
Merging interference cases for consecutive RBs in the subspace BIS BW;
And determining the candidate interference BW based on the merged interference cases.
9. The method of claim 8,
Wherein mapping the numbers of the interferers to the interference case comprises: if the number of the interferers is not mapped to a valid interference case, mapping the number of the interferers to at least one interference case, / RTI > comprising the steps of:
5. The method of claim 4, wherein the determining the interference DMRS sequence comprises:
Generating all possible DMRS sequences for the candidate interference BW;
Generating the interfering DMRS sequence by performing DMRS detection on all possible DMRS sequences.
A network device in a wireless communication system,
Estimating a parameter related to the interference based on the received signal from which the target signal is removed, estimating an interference signal based on the parameter related to the interference, removing the target signal of the target bandwidth (BW) from the received signal, And removing the interference signal from the received signal.
12. The method of claim 11,
Wherein the processor is operable to remove the target signal from the received signal if decoding of the received signal fails.
12. The method of claim 11,
And the processor estimates the parameter related to the interference based on the received signal from which the interference signal has been removed, if the decoding fails, decoding the received signal from which the interference signal has been removed.
12. The method of claim 11,
The processor determines a BIS BW by expanding the target BW based on energy for each of the resource blocks RBs and determines the RBs of the subspace BIS BW Determining at least one candidate interference BW based on the number of interferers for each of the candidate interference BWs, and determining at least one DMRS sequence by performing DMRS detection on the candidate interference BW.
15. The method of claim 14,
The processor detects energy for at least one RB before the starting RB and ending RB of the target BW and adding the at least one RB to the target BW based on a comparison result between the energy and a predetermined reference value And determines the partial space BIS BW.
15. The method of claim 14,
Wherein the processor determines at least one first eigenvalue, at least one second eigenvalue and at least one third eigenvalue for a pair of RBs for consecutive RBs in the subspace BIS BW, Determining the number of interferers for each of the RBs and the number of interferers for the pair of BSs based on a result of comparison between the first to third eigenvalues and a predetermined reference value, And determines the candidate interference BW based on the number of interferers for the pair of BSs.
17. The method of claim 16,
Wherein the first and second eigenvalues are determined based on covariance matrices for the consecutive RBs and the third eigenvalue is determined based on a common covariance matrix for the consecutive RBs.
17. The method of claim 16,
Wherein the processor maps the numbers of interferers for consecutive RBs to interference cases in the candidate interference BW, merges interference cases for consecutive RBs in the subspace BIS BW, To determine the candidate interference BW.
19. The method of claim 18,
Wherein the processor maps the numbers of the interferers to an interference case where some of the interferers are the same or similar when the number of interferers is not mapped to a valid interference case.
15. The method of claim 14,
Wherein the processor generates the all possible DMRS sequences for the candidate interference BW and performs the DMRS detection on all possible DMRS sequences to generate the interfering DMRS sequence.

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